Educational Codeforces Round 34 (Rated for Div. 2) D. Almost Difference（高精度）

题目链接：http://codeforces.com/contest/903/problem/D

题目不难，按每个元素算贡献就好了，就是会爆long long，学习一下py的写法

代码：

from collections import Countern = input()a = map(int, raw_input().split())s = 0c = Counter()for i in xrange(n):    s += c[a[i] + 1] - c[a[i] - 1] + a[i] * (2 * i + 1 - n)    c[a[i]] += 1print(s)